Not OP, but a big Nim fan. I think Nim has made a mistake by marketing itself as Python inspired. I know why it does so; Python is a very successful language and as a niche language, Nim wants to associate itself with an established one. But in my experience, Nim has a very small overlap with Python. It is whitespace significant, prefers short words to symbols for operators, and has a robust stdlib. But if you look at the actual language semantics, or even the keywords, Nim is not really related to Python. I'd go as far as saying Nim is more similar to a Lisp than it is Pythonic (which works fine for me, as I prefer Lisp to Python).

All of this to say, the OPs language seems much more Pythonic. The key words, the built in functions, the class system, all seems designed to match Python as closely as possible.

It's a wide question, and I don't have a good answer. One obvious difference is the syntax. I prefer Python's syntax over Nim's, but at the same time I find Python slow sometimes and hard to use in embedded systems. I'm aiming to create something similar to Nim's toolchain to address that.